This invention relates to dielectric ceramics. More particularly, this invention relates to dielectric ceramics having the composition of BaO-TiO.sub.2 -Sm.sub.2 O.sub.3 type.
In the region of microwave frequencies, dielectrics have conventionally been utilized in impedance matching and dielectric resonators. With the recent progress in the microwave field, particularly in the technology of integrated microwave circuit, efforts have been made actively in the interested circle to promote miniaturization by utilizing a dielectric resonator, in which dielectric ceramics with a high dielectric constant and low loss are used for stabilizing the frequency of an oscillator.
As a dielectric material suitable for these uses, a BaO-TiO.sub.2 type ceramic, a ceramic obtainable by partially replacing it with another element or a dielectric material obtainable by combining TiO.sub.2 having a negative temperature coefficient of dielectric constant with dielectric ceramics or glass having a positive temperature coefficient of dielectric constant in order to control said temperature coefficient has hitherto been used in many cases. However, these materials have many practical problems such as low dielectric constant, high dielectric loss, difficulty of obtaining a product having the desired temperature coefficient when used as a dielectric resonator, and so on.